1. Field of the Invention
The present invention relates to a composition in the form of a cream composed of a water-in-oil (W/O) emulsion having a high content of wax and to its uses in the cosmetics and dermatological fields. The invention also relates to methods of for caring for, treating and/or making up the skin and/or mucous membranes, and more particularly in the treatment of wrinkles and/or fine lines of the skin and/or in the treatment of dry skin. The invention also relates to a process for the preparation of the composition, wherein at least one stage of the process is carried out using a mixer-extruder.
2. Discussion of the Background
It is known to use waxes in cosmetic creams which are provided in the form of emulsions for caring for human skin, in particular for the anti-wrinkle effects of these waxes. Nevertheless, it is difficult to incorporate a high percentage of waxes in such compositions because waxes have a tendency to greatly thicken emulsions. In addition, when a high percentage of waxes is incorporated in an emulsion, the emulsion is very difficult to apply to the skin because it does not slip. Furthermore, a rough effect is produced on the skin. As a result, both the attractiveness and effective use of such an emulsion is significantly and undesirably reduced.
It is also known to incorporate a high percentage of waxes in mascaras. However, because of the above-mentioned disadvantages, compositions of this type cannot be used as a care product.
To prepare an emulsion that contains waxes, it is necessary to melt the e waxes in the fatty phase of the emulsion. This is particularly so if, for example, one wishes to use waxes having particularly advantageous anti-wrinkle effects on the skin, such as carnauba waxes. It is therefore necessary to heat the fatty phase to temperatures of 80-85xc2x0 C., which is particularly harmful if one wishes to incorporate heat-sensitive compounds into the composition.
The need therefore remains for a composition having the consistency of a cream and containing a significant percentage of waxes without the disadvantages of the prior art.
Surprisingly, it has now been found that it is possible to incorporate a high percentage of waxes in creams in the form of W/O emulsions, while retaining satisfactory fluidity and a pleasant feeling during application on the skin, by preparing the emulsion under cold conditions using a silicone emulsifier and starting from a soft oily phase having a high percentage of waxes.
Thus, one object of the present invention is to provide a composition having the consistency of a cream.
Another object of the invention is to provide a composition having a significant percentage of waxes without the above-mentioned disadvantages.
Another object of the invention is to provide a composition having a high percentage of waxes in creams in the form of W/O emulsions.
Another object of the invention is to provide a composition having satisfactory fluidity and a pleasant feeling during application on the skin,
These and other objects of the invention have been achieved by the present invention, the first embodiment of which provides a composition in the form of a cream composed of a water-in-oil emulsion that includes an aqueous phase dispersed in an oily phase, wherein it includes at least 25% by weight of an aqueous phase with respect to the total weight of the composition, at least one silicone emulsifier and at least 5% by weight of one or more waxes with respect to the total weight of the composition.
Another embodiment of the invention provides a cosmetic and/or dermatological composition, that includes the above composition.
Another embodiment of the invention provides a method of treating, protecting, caring for and/or cleansing the skin, mucous membranes and/or hair and/or in making up the skin and/or mucous membranes, that includes applying to the skin, mucous membranes and/or hair the above composition.
Another embodiment of the invention provides a method of treating wrinkles and/or fine lines of the skin, that includes applying to the skin the above composition.
Another embodiment of the invention provides a method of treating and/or protecting dry skin, that includes applying to the skin the above composition.
Another embodiment of the invention provides a process for preparing the above composition, that includes at least one step using a screw mixer-extruder.
Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description of the preferred embodiments of the invention.
The composition of the invention is in the form of a cream, that is to say a soft product, in contrast to a solid product, such as a stick. In the context of the present invention, a cream preferably has a viscosity at ambient temperature (approximately 20-25xc2x0 C.) ranging from approximately 1 to 25 Paxc2x7s and preferably from approximately 1 to 10 Paxc2x7s, this viscosity being measured with a Rheomat 180.
The composition of the invention, although containing a high level of wax, also contains a significant level of aqueous phase and is therefore fresh on application. In addition, since the mixing of the aqueous phase and the oily phase is carried out under cold conditions, heat-sensitive compounds can be incorporated without fear of their decomposition.
Preferably, the composition of the invention contains, in the oily phase, at least 5% by weight of one or more waxes with respect to the total weight of the composition. The cooled oily phase, before it is mixed with the aqueous phase, preferably exists in the form of a soft paste at ambient temperature (approximately 25xc2x0 C.). The term xe2x80x9csoft pastexe2x80x9d is understood here to mean a paste for which the viscosity can be measured, in contrast to the solid structure of a tube or stick, for which the viscosity cannot be measured. The dynamic viscosity of the soft paste at 25xc2x0 C. is generally between 3 and 35 Paxc2x7s, measured with a Contraves TV rotary viscometer equipped with an xe2x80x9cMS-r4xe2x80x9d rotor at a frequency of 60 Hz.
Preferable waxes which can be used in the composition of the invention include, for example, mineral waxes, such as microcrystalline waxes, paraffin wax, petrolatum wax, petroleum wax, ozokerite or montan wax; animal waxes, such as beeswax, lanolin and its derivatives; vegetable waxes, such as candelilla, ouricurry, carnauba or japan waxes, cocoa butter, or cork fibre or sugar cane waxes; hydrogenated oils which are solid at 25xc2x0 C.; fatty esters and glycerides which are solid at 25xc2x0 C.; synthetic waxes, such as polyethylene waxes and waxes obtained by the Fischer-Tropsch synthesis; silicone waxes, and their mixtures.
According to a preferred embodiment of the invention, use is made of at least one wax having a starting melting temperature greater than or equal to 50xc2x0 C. and better still at least one wax for which the starting melting temperature is greater than 65xc2x0 C., such as carnauba wax, some polyethylene waxes and some microcrystalline waxes, such as that sold by the company Tisco under the name xe2x80x9cTisco Wax 881, or that sold by the company RMC under the name of xe2x80x9cFeruwax 30540xe2x80x9d.
Preferably, the term xe2x80x9cstarting melting temperaturexe2x80x9d is understood to mean the temperature at which a wax begins to melt. This temperature can be determined by DTA (differential thermal analysis), which makes it possible to obtain a thermogram (or melt curve) of the wax under consideration. The starting melting temperature corresponds to the temperature at which a significant change of slope in the thermogram can be observed. The melting point, for its part, represents the minimum point in the thermogram.
The amount of wax(es) in the composition of the invention is at least 5% and preferably ranges from 5 to 30% and better still from 5 to 15% by weight with respect to the total weight of the composition. These ranges include all subranges and values therebetween.
The amount of oily phase containing at least one wax in the composition of the invention preferably ranges from 20 to 75% and more preferably from 30 to 60% by weight with respect to the total weight of the composition. These ranges include all subranges and values therebetween. Preferably, this oily phase is used in such an amount or else includes an amount of waxes such that the amount of waxes in the final composition is equal to or greater than 5%.
Preferably, the oily phase of the composition of the invention includes, in addition to the wax or waxes, one or more fatty substances chosen from oils of animal origin, oils of vegetable origin, mineral oils, synthetic oils, fluorinated oils, silicone oils, in particular volatile silicone oils, silicone gums, silicone resins, fatty alcohols, fatty acids and silicone elastomers, such as the products sold under the name xe2x80x9cKSGxe2x80x9d by the company Shin-Etsu, under the name xe2x80x9cTrefilxe2x80x9d by the company Dow Corning or under the name xe2x80x9cGransilxe2x80x9d by the company General Electric.
The silicone emulsifier used in the composition of the invention is preferably chosen from the group including oxyethylenated and/or oxypropylenated polydimethylsiloxanes, oxyethylenated and/or oxypropylenated (C10-C22)alkylpolydimethylsiloxanes (xe2x80x9c(C10-C22)alkylxe2x80x9d meaning that the alkyl chain contains from 10 to 22 carbon atoms), oxyethylenated and/or oxypropylenated polydimethylsiloxanes with glucoside groups, and their mixtures. These polydimethylsiloxanes can optionally be crosslinked. Preferably, the above-noted glucoside groups are bonded to the oxyethylenated and/or oxypropylenated polydimethylsiloxanes according to methods within the ordinary skill of the artisan.
Preferably, the silicone emulsifier can be introduced as is or as a mixture with a volatile or non-volatile silicone oil, such as a cyclomethicone (cyclohexasiloxane, cyclopentasiloxane or cyclotetrasiloxane).
Mention may be made, as the most preferred silicone emulsifiers which can be used in the composition of the invention, of the mixtures of dimethicone copolyol and of cyclomethicone sold under the names xe2x80x9cQ2-3225Cxe2x80x9d and xe2x80x9cDC2-5225Cxe2x80x9d by the company Dow Corning, the product sold under the name xe2x80x9cSF-1288xe2x80x9d by the Company General Electric, the polyglyceryl-4 isostearate/cetyl dimethicone copolyol/hexyl laurate mixture sold under the name xe2x80x9cAbil WE 09xe2x80x9d by the company Goldschmidt, the cetyl dimethicone copolyol sold under the name xe2x80x9cAbil EM 90xe2x80x9d by the company Goldschmidt, or the laurylmethicone copolyol sold under the name xe2x80x9cQ2-5200xe2x80x9d by the company Dow Corning.
The amount of silicone emulsifier in the composition according to the invention preferably ranges from 0.1 to 10% by weight as active material and more preferably from 2 to 5% by weight as active material with respect to the total weight of the composition. These ranges include all subranges and values therebetween.
The composition of the invention may additionally, and optionally, include one or more fillers (pulverulent constituents) which can be chosen, for example, from the group including talc; micas of natural or synthetic origin; kaolin; zinc or titanium oxides; calcium carbonate; magnesium carbonate and hydrocarbonate; silica, in particular spherical silica, silica powder, sold under the name xe2x80x9cCab-O-Sil TS 5301, by the company Cabot, and silica microbeads, such as those sold under the name SB 150 by the company Myoshi; titanium dioxide; glass and ceramic beads sold by the company 3M under the trade name xe2x80x9cMacrolitexe2x80x9d; metal soaps derived from an organic carboxylic acid having from 8 to 22 carbon atoms, preferably from 12 to 18 carbon atoms, for example zinc, magnesium or lithium stearate, zinc laurate or magnesium myristate; powders formed from non-expanded synthetic polymers, such as powders formed from polyethylene, polystyrene, polyesters, polyamides (for example, Nylon or poly-xcex2-alanine), acrylate copolymers (for example, the microporous microspheres sold by the company Dow Corning under the trade name xe2x80x9cPolytrapxe2x80x9d), poly(methacrylic acid)s, polystyrene or Teflon, such as xe2x80x9cFluonxe2x80x9d; expanded powders, such as hollow microspheres made of thermoplastic material prepared by known processes, such as those disclosed in U.S. Pat. No. 3,615,972 and EP-A-056,219 (the entire contents of each of which are hereby incorporated by reference), and in particular the microspheres sold under the trade name xe2x80x9cExpancelxe2x80x9d by the company Kemanord Plast or under the trade name xe2x80x9cMicropearl F 80 EDxe2x80x9d by the company Matsumoto; powders formed from natural organic materials, such as maize, wheat or rice starches, which may or may not be crosslinked, such as the powders formed from starch crosslinked by octenylsuccinic anhydride sold under the name xe2x80x9cDry-Floxe2x80x9d by the company National Starch; silicone resin microbeads, such as those sold under the name xe2x80x9cTospearlxe2x80x9d by the company Toshiba Silicone, and their mixtures.
Preferably, the fillers can represent up to 20% by weight with respect to the total weight of the composition and more preferably from 1 to 12% by weight with respect to the total weight of the composition. These ranges include all subranges and values therebetween.
The aqueous phase of the composition of the invention represents at least 25% by weight with respect to the total weight of the composition and preferably from 40 to 70% by weight with respect to the total weight of the composition. These ranges include all subranges and values therebetween.
The composition according to the invention can be used in any field where this type of pharmaceutical dosage form is advantageous and in particular in the cosmetics and dermatological fields. When it constitutes a cosmetic and/or dermatological composition, it may additionally include a physiologically acceptable medium, that is to say a medium which is compatible with the skin, mucous membranes, nails and/or hair.
Preferably, the compositions of the invention are especially suited for a large variety of treatments of the skin, mucous membranes (lips) and hair, including the scalp, in particular in protecting, caring for, cleansing and/or making up the skin and/or mucous membranes, in protecting, caring for and/or cleansing the hair and/or in the treatment of the skin, hair and/or mucous membranes.
The compositions according to the invention can be used, for example, as products for treating, caring for, protecting and/or cleansing the skin, in the form of creams or milks, or as (skin and lip) makeup products by incorporating fillers and/or coloring materials (pigments and/or dyes). They are particularly appropriate in the treatment of wrinkles and/or fine lines of the skin and in the treatment and/or protection of dry skin.
Another preferred embodiment of the invention relates to the cosmetic use of the composition as defined above in treating, protecting, caring for and/or cleansing the skin, mucous membranes and/or hair and/or in making up the skin and/or mucous membranes.
Another preferred embodiment of the invention relates to the cosmetic use of the composition as defined above in treating wrinkles and/or fine lines of the skin.
Another preferred embodiment of the invention relates to the use of the composition as defined above in the manufacture of a composition intended for treating and/or protecting dry skin.
In addition, and in a known way, the composition of the invention can additionally, and optionally, include adjuvants which are conventional in the cosmetics or dermatological field, such as hydrophilic or lipophilic active principles, preservatives, antioxidants, fragrances, solvents, sunscreen agents, coloring materials, basic or acidic agents, and lipid vesicles. These adjuvants are preferably used in the proportions which are conventional in the cosmetics or dermatological field, for example from 0.01 to 30% of the total weight of the composition, and they are, depending in their nature, introduced into the aqueous phase or into the oily phase of the composition or alternatively into vesicles. These adjuvants and their concentrations must be such that they do not modify the property desired for the composition.
Mention may be made, as preferred active principles which can be used in the composition of the invention, of, for example, moisturizing agents, such as polyols and in particular glycerol, ethylene glycol, isoprene glycol, 1,2-propanediol, diglycerol, sorbitol, polyethylene glycols and their mixtures.
Preferably, the composition according to the invention can advantageously be prepared by using, for at least one stage of the process, a kneading device, such as a roll-mill mixer comprising two rollers rotating in opposite directions, between which the paste passes, or a screw mixer-extruder. Use is preferably made of a screw mixer-extruder. More preferably, this step includes mixing and extruding or rolling and milling at least one or more of the constituent components of the composition of the invention, including the aqueous phase, the oily phase, the silicone emulsifier, or the wax(es), or mixtures thereof. Most preferably, the step includes mixing and extruding the wax(es) and the oils.
Another preferred embodiment of the invention provides a process for the preparation of a composition according to the invention, wherein at least one stage of the process is carried out using a screw mixer-extruder.
Preferably, according to a first embodiment of the invention, the preparation process includes the following stages:
(1) preparation of the oily phase in the form of a soft paste obtained by forming a premix of the waxes and oils, by heating this premix to a temperature at which it melts to form a molten premix, introducing the molten premix and preferably other constituents (most preferably the fillers) of the oily phase, all at once or in several portions, into a screw mixer-extruder and subjected to a temperature gradient ranging from 80xc2x0 C. to 20xc2x0 C. to form a mixture, kneading the mixture thus obtained while cooling it to ambient temperature while conveying it to the outlet of the mixer-extruder;
(2) incorporation of the silicone emulsifier into the soft paste obtained in (1); and
(3) incorporation, with stirring, of the aqueous phase into the mixture obtained in (2).
In the above-mentioned first embodiment, stages (2) and (3) are preferably carried out in a mixing device commonly used by a person skilled in the art, such as a rotor-stator.
Moreover, in the process described above, the amounts used are such that the emulsion obtained contains at least 5% by weight of wax and at least 25% by weight of aqueous phase, with respect to the total weight of the composition.
As indicated above, since the mixing of the oily and aqueous phases takes place under cold conditions, the incorporation of heat-sensitive compounds does not present a problem.
According to a most preferred embodiment of the invention, stages (2) and (3) above are also carried out in the screw mixer-extruder used for stage (1). The silicone emulsifier and the aqueous phase are then introduced into a part (or section) of the mixer-extruder where the temperature is close to ambient temperature.
The use of a mixer-extruder makes it possible to reproducibly obtain an oily phase paste of consistently high quality. In addition, it is possible, by adapting the outlet die of the mixer-extruder, to package the composition in line at the outlet of the said mixer-extruder.
Preferably, the various stages of the process can be carried out in one or more extruders arranged one after the other and more preferably in a single twin-screw extruder.
The preferred conditions under which the extrusion can be carried out are disclosed in the document FR-A2,715,306, the entire contents of which are hereby incorporated by reference.